Position signal transmitters of the above mentioned type are generally known, and are used in a variety of different applications for providing a feedback or answer-back indication of the end position of a member such as an armature that is movably operated by a servo drive. The servo drive, for example, includes a through-going shaft that protrudes from one side of the servo drive to provide a drive shaft for the armature and protrudes from the other side of the servo drive to provide an operating shaft that rotates absolutely synchronously with the drive shaft. The signal transmitter, also known as a position repeater or position feedback indicator, is coupled to the operating shaft to be operated absolutely synchronously with the rotational drive shaft of the servo drive. The dimensions of the protruding operating shaft as well as mounting holes provided on the side of the servo drive for securing the feet of the signal transmitter are standardized, to allow convenient coupling and mounting of the signal transmitter onto the servo drive.
In order to allow the signal transmitter to be adjusted in consideration of the actually existing armature position at the time and place of installation, it is necessary that the switching cams or other switching elements are selectively positionable among a plurality of different angular positions relative to the angular position of the switching shaft. It is known to secure the switching cams or switching elements onto the shaft in a form-locking manner by providing a respective gearing for these respective components. For example, the switching cams or switching elements are provided with an internal gearing, while area of the switching shaft is provided with an external gearing that meshes with the internal gearing of the switching cams or switching elements. Throughout this specification, a "gearing" simply refers to a series or set of gear teeth, which may have any known configuration. In order to nonetheless provide the necessary adjustability of the relative angular position of the cams or the like, the switching shaft must further have a non-geared area adjacent to the externally geared area, and the switching cams or switching elements must be axially slidable off of the externally geared area and onto the non-geared area, where the switching cams or switching elements are then rotatable relative to the switching shaft to achieve the desired rotational adjustment. Then the switching cams are axially pushed back onto the externally geared area of the switching shaft in order to provide the necessary form-locking connection.
It has been found in practice that the above manner of adjusting the rotational position is complicated and impractical, especially when several switching cams or switching elements are arranged axially one above the other. For example, especially if the lowermost switching cam or switching element must be adjusted, it is necessary to axially slide up all of the switching cams or switching elements and thereby disengage all of the switching cams or switching elements from the shaft, just to be able to rotationally adjust the lowermost one of the cams or switching elements. While carrying out this procedure, it can easily occur that one or more of the upper switching cams or elements, which were previously in the correct rotational position, are inadvertently replaced in a wrong rotational position due to their disengagement and renewed engagement with the externally geared portion of the switching shaft. Thus, it becomes necessary to check and ensure the correct angular repositioning of all of the switching cams when the intention was just to reposition the lowermost one of the cams.
The prospectus or brochure Nr. Z1-C-02-237, published by the company "bar GmbH" of Germany, discloses that it is known to provide planet gears for the switching cams for allowing the rotational adjustability. By using a tool, such as a screwdriver, it is possible to press down and then rotate adjustment screws, whereby the respective planetary gearing and therewith also the switching cam can be adjusted. While the adjustment of the switching cams is comparatively easy in this known signal transmitter, the construction of the switching cams provided with a planetary gearing is complicated, and therefore manufacturing the arrangement is expensive.
A further manner of adjusting the switching cams is also known, whereby the switching cams are respectively provided with an end face gearing or spur gearing that respectively cooperates with a corresponding end face gearing or spur gearing provided on an offset shoulder of the switching shaft. An axially acting spring presses the two corresponding spur gearings into engagement with one another, which thereby causes a non-rotational connection, i.e. a connection that does not allow relative rotation, between the switching cam and the switching shaft. In order to carry out a rotational adjustment of the switching cam, the switching cam can be pushed away from the spur gearing provided on the shaft, against the spring force, whereupon the switching cam is rotated into the desired rotational position and then released so that the spring force again pushes the cam into engagement with the spur gearing of the shaft to re-establish a form-locking connection therebetween without the application of any external force.
Carrying out the above described adjustment is, however, rather impractical because it can be rather difficult to manually slide or push the switching cams in the axial direction against the effect of the biasing springs and then rotate the switching cams while maintaining the pressure against the spring force. This is especially difficult under tight space conditions, whereby especially the various components installed within the housing of the signal transmitter all become a great hindrance. Moreover, the absolute size of each of the switching cams as well as the overall housing is rather small, so that carrying out the adjustment accurately requires a considerable level of skill and fine fingertip feeling and control.
Another problem that arises in conventional position signal transmitters is that it becomes rather complicated and difficult to properly mount and connect the mechanical or inductive switches in the housing, due to the tight or cramped space conditions within the housing, and due to the small size of the individual components. A pre-assembly of the switches simultaneously with the assembly or manufacturing of the signal transmitter is not possible because different types of switches must be selected from among a great number of standard switch types, depending on the particular application and the special needs of the ultimate user of the position signal transmitter.
In an attempt to address the above problem, the above mentioned brochure No. Z1-C-02-237 of the company "bar GmbH" discloses an arrangement in which the switches as well as further electrical or electronic components are pre-mounted on a mounting plate. With such a known arrangement, the standardized mounting plate always has the same dimensions and two mounting holes adapted to receive mounting screws that are screwed into corresponding threaded holes provided in the floor of the housing. However, the problem remains that the arrangement of components on the mounting plate is variable and must be adapted to the individual needs of the respective ultimate user of the device in each case. Thus, the simplified assembly and wiring of the switches can only be achieved in combination with the serious disadvantage that a plurality of differently prepared mounting plate arrangements must be manufactured and stored in inventory in order to meet the needs of consumers of the device. This leads to high costs for the production and the inventory of the devices.